珠江三角洲区域地下水盐运移的数值模拟
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摘要
珠江三角洲地下水资源潜力和地下水环境问题日益受到重视,但是区域地下水流场和水化学演变特征的研究程度较低。该地区濒临南海,第四系含水层随着三角洲沉积条件的变化,经历了多次海进海退的作用,形成了以底部砂砾石层为强透水层,以淤泥质粘土夹砂为弱透水盖层的含水层体系,地下水的矿化度总体较高。在此背景下,研究了珠江三角洲区域地下水流场和淡水驱替盐分运移的问题。
通过综合考虑区域地质构造以及第四系沉积特征,依据300多个钻孔数据,构建了珠江三角洲第四系含水层空间结构模型:取沉积相和地层年代划分为6层;取水文地质属性划分为4层。其中,最底部的砂砾石层是有供水意义的含水层,其粘性土覆盖层中砂体的分布与古河道有关。运用微水试验分析方法对粘性土中的抽水试验进行了研究,获得了粘性土的渗透系数。结果表明,研究区粘性土的渗透系数非常小,数量级为10~(-4)~10~(-5) m/d。根据珠江三角洲古河道的发育特征,取自上游地区到达海岛的长约180 km的投影剖面,绘制了垂向上的含水层结构,作为剖面二维分析的基础。以MODFLOW为模拟工具,对投影剖面上的地下水流场和盐分运移进行了数值模拟,发现存在多级流动系统,地表淡水1000年的驱替最大深度约20 m。多层结构的准三维地下水流模拟表明,区域地下水主要受地表水控制,水力梯度较小,淡水在砂砾石层的水平驱替速率最大可以达到66 km/万年。
对于古河道的影响、沉积历史在建模过程中的考虑、海底含水层的处理等问题,进行了专门的讨论。
The potential groundwater resources and associated environmental issues in Pearl River Delta attract increasingly attention. However, the knowledge of regional groundwater flow and evolution patterns of groundwater chemistry are still weak. The studied area is located nearby South China Sea. The Quaternary sediments have experienced several times between transgression and regression with the changes of sea level. As a result, the Pearl River Delta deposits form an aquifer system with a high permeable confined aquifer composed of gravel sand at the bottom and a low permeable confining unit composed of silty clay, silty sand and sand interbeds. In addition, salinity of groundwater is generally high. On the basis of this background, the patterns of regional groundwater flow and salt transport driven by freshwater infiltration in Pearl River Delta are studied.
According to the regional geological structure and Quaternary sedimentary characteristics as well as more than 300 boreholes data, a spatial structure model of the aquifer system is built up. The strata can be divided into 6 layers in considering of sedimentary facies and chronological age. However, the sediments can be classified into 4 layers for numerical modeling in considering of their hydrogeological properties. In these layers, only the gravel sand layer at the bottom has significant for water supply. Distribution of sands in its clayey confining unit is controlled by paleo-rivers. The hydraulic conductivity of clay is obtained through investigation of pumping test data with slug-test analysis method. It is indicated that the hydraulic conductivity of silt is small, with an magnitude of 10~(-4)~10~(-5) m/d. Along a main direction of paleo-river in Pearl River Delta, a typical reference profile from the upper-stream to a island in the sea is selected and drawn with aquifer systems. The length of the profile is about 180 km. The steady state groundwater flow and salt transport on the profile is simulated with MODFLOW, it is found that multi-flow systems develop on the profile and the maximum penetrating depth of fresh water is 20 m with respect to 1000-years transport. The multi-layers quasi-three-dimensional modeling of regional groundwater flow shows a pattern of flow filed that dominated by distribution of surface water. Hydraulic gradient in horizontal is small. The fresh water front can moves in the gravel sand aquifer to a maximum distance of 66 km, in ten thousand years, from its source area.
At last, the impacts of paleo-river channels, the role of sedimentary history in the modeling process and the treatment of submarine aquifer are discussed.
通过综合考虑区域地质构造以及第四系沉积特征,依据300多个钻孔数据,构建了珠江三角洲第四系含水层空间结构模型:取沉积相和地层年代划分为6层;取水文地质属性划分为4层。其中,最底部的砂砾石层是有供水意义的含水层,其粘性土覆盖层中砂体的分布与古河道有关。运用微水试验分析方法对粘性土中的抽水试验进行了研究,获得了粘性土的渗透系数。结果表明,研究区粘性土的渗透系数非常小,数量级为10~(-4)~10~(-5) m/d。根据珠江三角洲古河道的发育特征,取自上游地区到达海岛的长约180 km的投影剖面,绘制了垂向上的含水层结构,作为剖面二维分析的基础。以MODFLOW为模拟工具,对投影剖面上的地下水流场和盐分运移进行了数值模拟,发现存在多级流动系统,地表淡水1000年的驱替最大深度约20 m。多层结构的准三维地下水流模拟表明,区域地下水主要受地表水控制,水力梯度较小,淡水在砂砾石层的水平驱替速率最大可以达到66 km/万年。
对于古河道的影响、沉积历史在建模过程中的考虑、海底含水层的处理等问题,进行了专门的讨论。
The potential groundwater resources and associated environmental issues in Pearl River Delta attract increasingly attention. However, the knowledge of regional groundwater flow and evolution patterns of groundwater chemistry are still weak. The studied area is located nearby South China Sea. The Quaternary sediments have experienced several times between transgression and regression with the changes of sea level. As a result, the Pearl River Delta deposits form an aquifer system with a high permeable confined aquifer composed of gravel sand at the bottom and a low permeable confining unit composed of silty clay, silty sand and sand interbeds. In addition, salinity of groundwater is generally high. On the basis of this background, the patterns of regional groundwater flow and salt transport driven by freshwater infiltration in Pearl River Delta are studied.
According to the regional geological structure and Quaternary sedimentary characteristics as well as more than 300 boreholes data, a spatial structure model of the aquifer system is built up. The strata can be divided into 6 layers in considering of sedimentary facies and chronological age. However, the sediments can be classified into 4 layers for numerical modeling in considering of their hydrogeological properties. In these layers, only the gravel sand layer at the bottom has significant for water supply. Distribution of sands in its clayey confining unit is controlled by paleo-rivers. The hydraulic conductivity of clay is obtained through investigation of pumping test data with slug-test analysis method. It is indicated that the hydraulic conductivity of silt is small, with an magnitude of 10~(-4)~10~(-5) m/d. Along a main direction of paleo-river in Pearl River Delta, a typical reference profile from the upper-stream to a island in the sea is selected and drawn with aquifer systems. The length of the profile is about 180 km. The steady state groundwater flow and salt transport on the profile is simulated with MODFLOW, it is found that multi-flow systems develop on the profile and the maximum penetrating depth of fresh water is 20 m with respect to 1000-years transport. The multi-layers quasi-three-dimensional modeling of regional groundwater flow shows a pattern of flow filed that dominated by distribution of surface water. Hydraulic gradient in horizontal is small. The fresh water front can moves in the gravel sand aquifer to a maximum distance of 66 km, in ten thousand years, from its source area.
At last, the impacts of paleo-river channels, the role of sedimentary history in the modeling process and the treatment of submarine aquifer are discussed.
引文
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Hendry, M.J., L.I. Wassenaar. Inferring Heterogeneity in Aquitards Using High-Resolution dD and d18O Profiles. Ground Water, 2009, 47(5): 639~645.
J A Fyfe etc. Quaternary sea-level change on the continental shelf of Hong Kong. Journal of the Geological Society. 1997, Vol.154
LI X D, WAI O, LI Y S,et al. Heavy metal distribution in sediment profiles of the Pearl River Delta estuary, South China, Applied Geochemistry, 2000,15(5)
Ortega G.A., Cherry J A, Aravena R. Origin of pore water and salinity in the lacustrine aquitard overlying the regional aquifer of Mexico City. Journal of Hydrology, 1997, 197: 46~69.
Parker, B.L., Aquitard Integrity and DNAPLs[A]. Abstract 201-11. 2004 GSA Abstracts with Programs, Denver, Colorado, 2004, 35(5), Nov. 7-10, p. 468.
Parker, B.L., J.A. Cherry, R.W. Gillham et al. Field and laboratory evidence of diffusive mass transfer rates from immiscible-phase organic liquids in clay Quaternary deposits. Session 100: Hydrogeology II: Quantitative Hydrogeology, Geological Survey of America Abstracts and Program p-76A-258, Boston, Mass, 1993, October 25~28.
T.Ludmann, How Kin Wong, Pinxian Wang. Plio-Quaternary sedimentation processes and neotectonics of the northen continental margin of the South China Sea. Marine Geology. 2001(172): 331~358
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YANG XiaoQiang, Rodney GRAPES, etc. Magnetic properties of sediments from the Pearl River Delta, South China: Paleoenvironmental implications. Science in China Series D: Earth Sciences. 2008, 51(1): 56~66
Zhan Xiaoyong, Simulation of unsteady flow and solute transport in a tidal river network, Source: Engineering Computations(Swansea, Wales), 2003, (20): 5~6
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狄效斌,孙继朝,荆继红,等.珠江三角洲地区地下水贮存特征及其开发前景分析.南水北调与水利科技,2008,6(6):52~56
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顾再仁,姚志坚.珠江口东片河网与伶仃洋潮流的数值模拟.人民珠江,1993,(3)
郭良田,李运贵.珠三角地区晚第四纪以来气候变化和海平面升降的耦合效应.华南地震,2008,28(2):53~58
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胡嘉镗,李适宇.珠江三角洲一维盐度与三维斜压耦合模型.水利学报,2008,39(11):1174~1182
黄冠星,孙继朝,荆继红,等.珠江三角洲地区地下水铁的分布特征及其成因,中国地质,2008,35(3):531~538
黄冠星,孙继朝,荆继红,等.珠江三角洲地区浅层地下水天然防污性能评价方法探讨.工程勘察,2008,(1):44~49
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黄镇国,张伟强,范锦春,等.珠江三角洲海平面上升的影响范围.海洋与湖沼,2001,32(2):225~232
贾国东,彭平安,傅家谟.珠江口近百年来富营养化加剧的沉积记录.第四纪研究,2002,22(2):158~165
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李远青.近20年来珠江三角洲网河区水文要素变化特征分析.广东水利水电,2010,8(8):54~57
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刘文新,李向东.珠江口沉积物中痕量金属富集研究.环境科学学报,2003,23(3):338~344
龙云作等.珠江三角洲沉积地质学.北京:地质出版社,1997
彭静,何少苓,廖文根,等.珠江三角洲大系统洪水模拟分析及防洪对策探讨.水利学报,2003(11):78~84
彭静,彭期冬.珠江河口三角洲数值模拟技术研究进展.水利水电技术,2005,36(10):78~82
沈珍瑶,谢彤芳.确定含水层渗透系数的微水试验法.地下水,1994,16(1):4-5
王珊珊.珠江三角洲和近岸河口海域现代沉积环境及晚更新世以来的环境演变.[博士学术论文]青岛:中国海洋大学,2008
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张景平,黄小平,江志坚,等.2006-2007年珠江口富营养化水平的季节性变化及其与环境因子的关系.海洋学报,2009,31(3):113~120
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诸裕良,严以新,李瑞杰,等河网海湾水动力联网数学模型.水科学进展2003,14(2):131~135
Hendry, M.J., and L.I. Wassenaar. Implications of the distribution of ?D in porewaters for groundwater flow and the timing of geologic events in a thick aquitard system. Water Resources Research 35, 1999, no. 6: 1751~1760.
Hendry, M.J., L.I. Wassenaar. Inferring Heterogeneity in Aquitards Using High-Resolution dD and d18O Profiles. Ground Water, 2009, 47(5): 639~645.
J A Fyfe etc. Quaternary sea-level change on the continental shelf of Hong Kong. Journal of the Geological Society. 1997, Vol.154
LI X D, WAI O, LI Y S,et al. Heavy metal distribution in sediment profiles of the Pearl River Delta estuary, South China, Applied Geochemistry, 2000,15(5)
Ortega G.A., Cherry J A, Aravena R. Origin of pore water and salinity in the lacustrine aquitard overlying the regional aquifer of Mexico City. Journal of Hydrology, 1997, 197: 46~69.
Parker, B.L., Aquitard Integrity and DNAPLs[A]. Abstract 201-11. 2004 GSA Abstracts with Programs, Denver, Colorado, 2004, 35(5), Nov. 7-10, p. 468.
Parker, B.L., J.A. Cherry, R.W. Gillham et al. Field and laboratory evidence of diffusive mass transfer rates from immiscible-phase organic liquids in clay Quaternary deposits. Session 100: Hydrogeology II: Quantitative Hydrogeology, Geological Survey of America Abstracts and Program p-76A-258, Boston, Mass, 1993, October 25~28.
T.Ludmann, How Kin Wong, Pinxian Wang. Plio-Quaternary sedimentation processes and neotectonics of the northen continental margin of the South China Sea. Marine Geology. 2001(172): 331~358
Wu,Chaoyu, J.Ren,Y.Bao, ect. Delta Evolution Patterns and the Associated Dynamic Environments of the Pearl River Estuaries Since Last Transgression. Jointmeeting of IGCP-475 DeltaMAP, APN Mega deltas in Asia, &CCOP DelSEA project
YANG XiaoQiang, Rodney GRAPES, etc. Magnetic properties of sediments from the Pearl River Delta, South China: Paleoenvironmental implications. Science in China Series D: Earth Sciences. 2008, 51(1): 56~66
Zhan Xiaoyong, Simulation of unsteady flow and solute transport in a tidal river network, Source: Engineering Computations(Swansea, Wales), 2003, (20): 5~6
陈崇希,李国敏.地下水溶质运移理论及模型.武汉:中国地质大学出版社,1996
陈崇希,林敏.地下水动力学.武汉:中国地质大学出版社,1999
陈坚雄.珠江三角洲水文监测站网优化与系统整体规划研究. [硕士学位论文]武汉:武汉大学,2004
陈伟光,赵红梅,常郁,等.珠江三角洲晚第四纪垂直构造运动速率.地震地质,2001,23(4):581~587
成建梅,李国敏,陈崇希.滨海、海岛海水入侵数值模拟研究.武汉:中国地质大学出版社,2004
狄效斌,孙继朝,荆继红,等.珠江三角洲地区地下水贮存特征及其开发前景分析.南水北调与水利科技,2008,6(6):52~56
地质矿产部第二海洋地质调查大队.珠江三角洲沉积特征及沉积模式.广州:地质矿产部海洋地质研究所,1987
董冬冬,王大伟,张功成,等.珠江口盆地深水区新生代构造沉积演化,中国石油大学学报(自然科学版),2009,33(5):17~23
董燕红,蔡建东,钱宏林.珠江口海域营养盐比及与浮游植物的关系.海洋通报,2009,28(1):3~10
方国祥,李平日,黄光庆.珠江三角洲8000年来海平面变化.地理研究,1991,10(4):1~11
顾再仁,姚志坚.珠江口东片河网与伶仃洋潮流的数值模拟.人民珠江,1993,(3)
郭良田,李运贵.珠三角地区晚第四纪以来气候变化和海平面升降的耦合效应.华南地震,2008,28(2):53~58
郭秀红.珠江三角洲地区浅层地下水有机污染研究. [博士学术论文]北京:中国地质大学(北京),2006
胡嘉镗,李适宇.珠江三角洲一维盐度与三维斜压耦合模型.水利学报,2008,39(11):1174~1182
黄冠星,孙继朝,荆继红,等.珠江三角洲地区地下水铁的分布特征及其成因,中国地质,2008,35(3):531~538
黄冠星,孙继朝,荆继红,等.珠江三角洲地区浅层地下水天然防污性能评价方法探讨.工程勘察,2008,(1):44~49
黄镇国,李平日,张仲英,等.珠江三角洲形成发育演化.广州:科学普及出版社广州分社,1982
黄镇国,张伟强,范锦春,等.珠江三角洲海平面上升的影响范围.海洋与湖沼,2001,32(2):225~232
贾国东,彭平安,傅家谟.珠江口近百年来富营养化加剧的沉积记录.第四纪研究,2002,22(2):158~165
李平日,乔彭年,郑洪汉,等.珠江三角洲一万年来环境演变.北京:海洋出版社,1991
李远青.近20年来珠江三角洲网河区水文要素变化特征分析.广东水利水电,2010,8(8):54~57
刘芳文,颜文,王文质,等.珠江口沉积物重金属污染及其潜在生态危害评价.海洋环境科学.海洋环境科学,2002,21(3):34~38
刘文新,李向东.珠江口沉积物中痕量金属富集研究.环境科学学报,2003,23(3):338~344
龙云作等.珠江三角洲沉积地质学.北京:地质出版社,1997
彭静,何少苓,廖文根,等.珠江三角洲大系统洪水模拟分析及防洪对策探讨.水利学报,2003(11):78~84
彭静,彭期冬.珠江河口三角洲数值模拟技术研究进展.水利水电技术,2005,36(10):78~82
沈珍瑶,谢彤芳.确定含水层渗透系数的微水试验法.地下水,1994,16(1):4-5
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